1. Field of the Invention
The present invention relates to a chemical mechanical polishing (CMP) pad conditioner having a substrate and a cutting tip pattern formed on at least one surface of the substrate.
2. Description of the Related Art
Currently, the speed and integration density of semiconductor circuits are increasing, and thus the size of semiconductor chips is gradually increasing. In addition, in order to provide multilayer interconnection structures, the width of interconnections is being minimized and the diameter of the wafers is becoming larger.
However, with an increase in the integration density of devices and a decrease in the minimum line width, limitations that cannot be overcome by partial planarization, according to the related art, have arisen. To enhance processing efficiency or quality, global planarization of wafers is performed by CMP. Global planarization by CMP is a necessary part of current wafer processes.
CMP is a polishing process in which a semiconductor wafer is planarized by chemical and mechanical treatment.
In principle, CMP polishing is performed by pressing a polishing pad and a wafer against each other and moving them with respect to each other while supplying a slurry consisting of a mixture of abrasive particles and chemicals to the polishing pad. Herein, a large number of pores on the surface of the polishing pad, which is made of polyurethane, serve to receive fresh polishing solution so that high polishing efficiency and uniform polishing of the wafer surface can be obtained.
However, because different pressures and relative speeds are applied during the polishing process, the surface of the polishing pad can become non-uniformly deformed with the passage of time during the polishing, and the pores on the polishing pad can become clogged with the polishing residue, wherein the polishing pad cannot perform its intended function. For this reason, uniform polishing of the wafer surface by global planarization cannot be accomplished.
To overcome the non-uniform deformation of the CMP polishing pad and the clogging of the pores of the CMP polishing pad, a CMP pad-conditioning process is performed by finely polishing the surface of the polishing pad using a CMP pad conditioner so as to form new pores on the pad.
The CMP pad conditioning process can be performed at the same time as the CMP process to increase productivity. This is so-called “in-situ conditioning”.
The polishing solution that is used in the CMP process contains abrasive particles, such as silica, alumina, or ceria, and the CMP processes are broadly classified into oxide CMP and metal CMP, according to the kind of polishing process used. The polishing solution that is used in oxide CMP generally has a pH of 10-12, and the polishing solution that is used in metal CMP has an acidic pH of 4 or less.
Conventional CMP pad conditioners include an electroplated-type CMP pad conditioner, manufactured by an electroplating process, and a melted-type CMP pad conditioner manufactured by melting a CMP pad conditioner and metal powder at high temperature.
However, these conventional electrodeposited-type and melted-type CMP pad conditioners have a problem in that, when they are used for in-situ conditioning in the metal CMP process, diamond particles attached to the surface of the CMP pad conditioners become detached from the surface via the action of polishing via the polishing particles of the CMP slurry and surface corrosion caused by the acidic solution.
When the detached diamond particles are stuck in the CMP polishing pad during the CMP polishing process, they scratch the water surface to increase process defect rates and make it necessary to replace the CMP polishing pad.
In addition, metal ions released from the metal binder via corrosion move to the metal line of a semiconductor circuit during the metal CMP process and can cause metal ion contamination, which causes short circuits. Because the short circuits caused by metal ion contamination are only revealed after all of the processes have been completed, the loss of production cost via the metal ion contamination is significant.
In an attempt to solve the above-described problems that occur in conventional CMP pad conditioners, Korean Patent Laid-Open Publication No. 2000-24453 discloses a polishing pad conditioner and a manufacturing method thereof. This patent publication discloses the processing of a substrate having a plurality of polygonal columns, which protrude from at least one surface thereof to substantially the same height, using a chemical vapor deposition (CVD) process, thereby forming a diamond thin film on the surface. Herein, the polygonal columns are the protruding cutting tips.
This polishing pad conditioner includes a plurality of cutting tips which protrude by substantially the same distance. These tips can produce minor cuts on a polyurethane polishing pad during a conditioning process, but cannot finely crush large debris generated during the conditioning process, nor efficiently sweep out the sludge that is generated from the wafer.
For such functions as these, the polishing pad conditioner should have, in addition to cutting tips for cutting the polishing pad, cutting tips that are of different heights, which reduce the size of debris generated during the conditioning process and make the flow of the sludge smoother.
FIG. 1 shows a conventional CMP pad conditioner 101 having cutting tips. As shown in FIG. 1, in order to form a plurality of independent cutting tip patterns 120 on a substrate 110, diamond is deposited on the substrate 110 and then patterned using an etching mask. Then, a diamond coating layer 130 is deposited on the cutting tip patterns 120.
However, this CMP pad conditioner has the following two problems. First, in order to form the cutting tip patterns on the substrate via the first diamond deposition process, a diamond layer should be formed on the substrate to a height corresponding to the height of the cutting tips.
Various processes are used to form a diamond deposition layer using a CVD process. Among them, a thermal filament process is generally used to form a substrate having a relatively large area, such as a CMP pad conditioner.
When the thermal filament process is used, a coating time of 100-200 hours is required to grow the diamond layer to a height of 30-60 μm, so as to form cutting tip patterns for a CMP pad conditioner, because the growth rate of diamond is as low as about 0.1-0.3 μm/hr. For this reason, the productivity of the CMP pad conditioner is significantly reduced.
Another problem is that diamonds have extremely low impact strength due to their high brittleness, even though diamonds have high hardness. Considering conditioner pressure and abrasion via friction with the polishing material, which occur via finely cutting the tip patterns during polishing of the polishing pad in the CMP system, the stability of the cutting patterns against breakage and detachment cannot be ensured. This breakage and detachment of the cutting tip patterns cause scratches to form on the silicon wafers.
Accordingly, it is important to ensure the impact stability of the cutting tip patterns. However, it is difficult to form fine cutting tip patterns having a size of 100 μm because CVD diamond layers grow into columnar structures that are very weak against the shear loads applied during the conditioning process.